LP3907 datasheet(21/57 Pages) TI1

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VIN

ENLDO

VLDO

GND

Vref

LDO

controlled

LP3907

www.ti.com

SNVS511N – JUNE 2007 – REVISED AUGUST 2011

DC/DC Converters

OVERVIEW

The LP3907 supplies the various power needs of the application by means of two Linear Low Drop Regulators

(LDO1 and LDO2) and two Buck converters (SW1 and SW2). The table hereunder lists the output characteristics

of the various regulators.

Table 3. Supply Specification

Output

Supply

Load

IMAX

VOUT Range(V)

Resolution (mV)

Maximum Output Current (mA)

LDO1

analog

1.0 to 3.5

100

300

LDO2

analog

1.0 to 3.5

100

300

SW1

digital

0.8 to 2.0

1000

SW2

digital

1.0 to 3.5

100

600

LINEAR LOW DROPOUT REGULATORS (LDOS)

LDO1 and LDO2 are identical linear regulators targeting analog loads characterized by low noise requirements.

LDO1 and LDO2 are enabled through the ENLDO pin or through the corresponding LDO1 or LDO2 control

programmed during Final Test, which can be tailored to the specific needs of the system designer.

NO-LOAD STABILITY

The LDOs will remain stable and in regulation with no external load. This is an important consideration in some

circuits, for example, CMOS RAM keep-alive applications.

LDO1 AND LDO2 CONTROL REGISTERS

LDO1 and LDO2 can be configured by means of the LDO1 and LDO2 control registers. The output voltage is

programmable in steps of 100mV from 1.0V to 3.5V by programming bits D4-0 in the LDO Control registers. Both

LDO1 and LDO2 are enabled by applying a logic 1 to the ENLDO1 and ENLDO2 pin. Enable/disable control is

also provided through enable bit of the LDO1 and LDO2 control registers. The value of the enable LDO bit in the

SW1, SW2: Synchronous Step-Down Magnetic DC/DC Converters

FUNCTIONAL DESCRIPTION

The LP3907 incorporates two high-efficiency synchronous switching buck regulators, SW1 and SW2, that deliver

a constant voltage from a single Li-Ion battery to the portable system processors. Using a voltage mode

architecture with synchronous rectification, both bucks have the ability to deliver up to 1000mA and 600mA,

respectively, depending on the input voltage and output voltage (voltage head room), and the inductor chosen

(maximum current capability).

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